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Me and Momma and Big John
Little John is proud of his mother's work as a stonecutter for a cathedral called \"Big John,\" but struggles to understand the importance of spending so much time on one stone that no one will know Momma cut. Includes a history of New York City's Cathedral of St. John the Divine.
Book
Tool wear detection of milling cutter based on heterogeneous data decision-level fusion
The traditional single-sensor approach for detecting tool wear in flat-end milling cutters presents limitations, often resulting in misdiagnoses and missed detections. To address this issue, this paper proposes a novel method that extracts time-frequency features from heterogeneous data and applies enhanced BP and ResNet neural networks for preliminary diagnosis. The improved D-S evidence theory is then employed for decision-level data fusion, achieving an average diagnostic accuracy of 95.60%, significantly surpassing the performance of single-method detection approaches.
Journal Article
A Failure Diagnosis Method of the Disc Cutter Based on ARIMA
As one of the main rock-breaking tools on the cutterhead of the shield machine, the disc cutter often fails due to the abnormal wear, which in turn affects the tunneling efficiency of the shield machine, in order to find and replace the failed disc cutter in time, a means to effectively detect the wear state and a method to diagnose the failure of the disc cutter are required.In this paper, a failure diagnosis method combining the disc cutter wear measurement and ARIMA prediction is proposed, the theoretical model of wear change law under three common wear forms such as the normal wear, the eccentric wear and the polygon wear were established, and realize the prediction of the disc cutter wear by data cleaning, time reconstruction, model ordering, residual test and other treatments of wear time series, and the error threshold of the disc cutter failure was set by experiment, and a failure diagnosis method of the disc cutter is constructed. The method was applied to an actual case, and the diagnostic accuracy is 83.3%.
Journal Article
Theoretical Research and Simulation Analysis on the Cutter Spacing of Double Disc Cutters Breaking Rock
The arrangement of disc cutter on a cutter head is important to improve the performance of TBM (tunnel boring machine) cutter, cutter life and cutter disc bearing life, then reduce vibration of TBM and reduce the noise. The rock breaking with double disc cutters is the basis of study on the distribution of disc cutter on cutter head, and it plays an important role on optimum arrangement of disc cutter on cutter head. In the process of rock breaking with double disc cutters, the axial vertical distance between two cutters is an important construction parameter, which directly affects rock breaking efficiency. Therefore, research on optimal cutter spacing and analysis of adaptability between cutter spacing and rock characteristics play an important role in optimizing the arrangement of cutter on the cutter head and improving the rock breaking efficiency of TBM. This paper analyzed the breaking rock force of double disc cutters. Taking granite samples as an example, the process of rock breaking with double disc cutters was simulated. Then rock fragmentation analysis based on different cutter spacing was carried out. Finally, the rock of different cutter spacing adaptability was studied. A series of conclusions about double disc cutters breaking rock were drawn.
Journal Article
Study on the design and cutting performance of stepped bi-directional milling cutters for hole making of CFRP
During hole making of carbon fiber reinforced plastic (CFRP) by helical milling, the tool wear is a main factor in machined surface damage, being unable to guarantee machining quality and accuracy, and restricting the improvement of hole making efficiency. In order to prolong the service life of cutters, this paper has carried out the research into the design, manufacture, and cutting performance of stepped bi-directional milling cutters, combining with hole making of CFRP by bi-directional helical milling. By the method of differential geometry, the geometric model of the profile shape and the mathematical model of the helical edge are established of the stepped bi-directional milling cutter. Additionally, based on the transformation matrix between grinding wheel and workpiece coordinates of any point, the track equation of grinding wheel is derived from grinding the side edge helical groove of the stepped bi-directional milling cutter. What is more, the grinding process and accuracy are measured about the designed stepped bi-directional milling cutter. The experiment of CFRP holes made by bi-directional helical milling is designed, and the experimental results show that the axial cutting force of stepped bi-directional milling cutters is smaller and fluctuates more gently than that of symmetrical bi-directional milling cutters in the backward milling. Especially, the former has better distributed and slower flank wear on the backward cutting edge, and better machining quality than the latter.
Journal Article
Research on automatic data acquisition scheme of tool profile wear based on B/S structure
As the core element in the production system of the manufacturing industry, the state of cutters directly affects the production quality and processing efficiency. Therefore, it is very meaningful to monitor the wear of machining cutters. This paper proposes an automatic data acquisition scheme based on the on-machine vision measurement device and B/S Internet structure technology. Finally, the round-nose milling cutter experiment verifies the scheme’s feasibility.
Journal Article
Study on design, manufacture, and cutting performance of circular-arc milling cutters for machining titanium alloy
Titanium alloy is widely used for manufacturing structural parts of high-end equipment due to its excellent mechanical properties, despite difficulty in being machined. Nowadays, titanium alloy parts are mostly machined by ball-end milling cutters (BEMC), but the cutting edge structure of the BEMC limits the improvement in machining efficiency and surface quality of the parts. In this paper, a circular-arc milling cutter (CAMC) with large-curvature cutting edge was proposed; the differential geometry method was used for establishing the geometric model for the contour surface of the CAMC and the mathematical model for the spiral cutting edge line; the conversion matrix between grinding wheel and workpiece coordinates was introduced to derive the equation of grinding wheel trajectory when the rake face of the CAMC was ground; the self-designed CAMC was ground and tested in accuracy. The comparative research was conducted experimentally on the side milling of titanium alloy TC4 with the CAMC and BEMC, and consequently the variation laws of milling forces, wear morphology, and machined surface quality were obtained about the two types of milling cutters. The results indicated that the CAMC can effectively reduce the main milling force and keep the milling process stable. Moreover, the CAMC was worn slower and produced better surface quality than the BEMC.
Journal Article
Comparative study on cutting performance of CFRP/Ti-laminated materials with flat end milling cutter and circular arc milling cutter in inclined angle milling
Carbon fiber reinforced polymer (CFRP) and titanium alloy (Ti-6Al-4V) have excellent mechanical properties and have been widely used in aviation, aerospace, and other fields. Due to the different characteristics of CFRP/Ti-laminated materials, there are differences in their processing parameters and material removal methods. Cutter wear and hole defects are prone to occur. To study the cutting performance of cutters in laminated materials, this paper adopts the inclined angle milling method to process CFRP/Ti-laminated materials. The cutting performance of flat end milling cutter and circular arc milling cutter was compared and analyzed through designed variable parameter experiments. A study was conducted on the axial force, cutter wear mechanism, hole quality, and micro-morphology of the hole wall of two cutters under the inclined angle milling method. The results show that under different processing parameters, the difference in axial force between the two cutters is small in the carbon fiber layer. However, there is a significant difference in the titanium layer, with the axial force of the circular arc milling cutter being smaller than that of the flat end milling cutter. As the number of holes increases, the wear of the flat end milling cutter is serious, and the cutting edge is broken. The wear area gradually expands from the cutter tip to the surrounding cutting edge. The wear of the circular arc milling cutter is relatively light, and the cutting edge is damaged. As the wear at the arc transition becomes dull, the wear area gradually extends to the surrounding cutting edge. As the cutters wear out, many burrs and tear damage appear at the CFRP exit of the flat end milling cutter. Many high burrs appeared at the exit of Ti-6Al-4V. Comparing the micro-morphology of the hole wall of the two cutters at different fiber cutting angles, the quality of the hole wall of the flat end milling cutter is worse than that of the circular arc milling cutter. Due to the arc transition structure of the circular arc milling cutter, the hole wall has obvious groove scratches, resulting in a decrease in the quality of the Ti-6Al-4V hole wall. In addition, compared with the flat end milling cutter, the surface roughness of the hole of the circular arc milling cutter is better.
Journal Article
Analysis and Enlightenment on the Relationships between Two Kinds of Cutter Life Evaluation Indexes and Installation Radius: A Case Study
Accurate evaluation of cutter life at different cutter positions on the cutter head is helpful to determine the time of cutter change and reduce the time of cutter wear measurement, which is of great significance to improve the tunneling efficiency of tunnel boring machine (TBM) projects. Unfortunately, there is no unified cutter life evaluation index now. The field data of cutter wear are collected from a section of a long TBM tunneling water conveyance tunnel in China. Two kinds of cutter life evaluation indexes (based on the radial wear extent of cutter rings and replacement number of cutter rings) are selected and the variation rule between these two kinds of indexes with cutter installation radius is statistically analyzed. The results show that the regression relationships between the two kinds of cutter life evaluation indexes and installation radius mainly present linear functions and quadratic functions. Those regression relationships are affected by factors such as wear type, installation angle, cutter spacing, influence width, and allowable limit wear extent of cutter rings. Considering the calculation accuracy of the evaluation index, the actual working conditions of the disc cutter, and ignoring the influence of tunnel diameter, it is recommended to preferentially choose the radial wear extent of cutter rings per unit rolling distance as the evaluation index of cutter life. The research results can provide a reference for the selection of cutter life evaluation index, prediction of disc cutter life at different cutter positions, and establishment of cutter life prediction mode.
Journal Article
Wear state detection of the end milling cutter based on wear volume estimation
The process of high-speed and high-precision machining is highly dependent on the wear process of the tool, so it is necessary to obtain the accurate identification of the wear state of the tool and the timely prediction of the degradation trend through effective detection methods. However, the influencing factors of the real cutting process are complex and variable. The milling process is a complex spatial deformation process, accompanied by very high cutting accuracy requirements, and it is hard to use VB value, the currently popular singular linear indicator of wear state evaluation, to describe the current wear state of end mills precisely and difficult to make a valid decision proof for subsequent dynamic degradation trends. For these issues, a three-dimensional wear region reconstruction and calculation method for end milling cutters based on bi-sensor monitoring information is proposed in this paper, which can be accurately used to estimate the volume of current wear areas and give more reasonable predictions of future wear trends. Firstly, an in situ wear detection device with a bi-sensor based on an industrial camera and line laser scanner is designed, which can obtain the wear shape and depth information synchronously with high precision. Secondly, aiming at the problem of missing wear information due to uneven furring wear on the rear tool face of the end milling tool, this paper proposes a combined threshold segmentation method to extract the complete tool wear region, which improves the calculation precision of the wear region. Thirdly, the SFS algorithm, which integrates high-precision scale information from line laser data, is utilized to reconstruct the rear tool surface topography. This reconstruction allows for accurate estimation of the wear volume. Finally, the experiment results have shown that the wear volume can reflect the wear state of the tool more quickly and comprehensively compared with the traditional tool wear width standard, and it can provide early warning before the tool enters severe wear condition.
Journal Article